The study examined marijuana users in the state of Washington. It was conducted on behalf of state officials to prepare for sale and taxation of marijuana.

“Information we collected from marijuana users in Washington prompted us to conclude that consumption is significantly larger than previously estimated,” said Beau Kilmer, the study's lead author.

Previously, state officials estimated that marijuana use in Washington would be 85 metric tons. Using new methods, the researchers concluded that marijuana use would instead be 175 metric tons.

In 2012, voters in Washington state passed an initiative allowing adults to possess up to one ounce of marijuana for non-medical use.

Understanding the size and composition of the marijuana market helped state officials to accurately project tax revenues for the state.

The proposed tax of 25% applies to producers, processors, and retailers. The revenues will be used to fund substances abuse treatment, prevention and research.

Researchers compiled the marijuana consumption estimates using a novel web-based survey. The survey displayed photographs of marijuana to help participants better report the actual quantity that they used.

According to researchers, previous studies underestimated the amount of marijuana consumed per person.

The RAND report also includes appendices that detail the study methodologies. This supplementary document also noted that the potency of marijuana has increased steadily since 1985.

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Brett Grodeck has written about health and medicine for over two decades. His articles have appeared in Chicago Magazine, the Chicago Reader, and Men's Fitness magazine. He's worked for the RAND Corporation, numerous health, medical device, and pharmaceutical companies, including consulting for the U.S. Food and Drug Administration. Contact Brett at this address.